Heat transfer tube for air conditioner application

ABSTRACT

A heat transfer tube and a heat exchanger incorporating at least one heat transfer tube are provided. The heat transfer tube and the heat exchanger are optimized for use within an air conditioner (which is configured to operate only in a cooling mode). The heat transfer tube includes a tube body with an interior surface and an exterior surface. The tube body defining an outer diameter (D o ) and a wall thickness (W T ), wherein a ratio (W T /D o ) the wall thickness (W T ) to the outer diameter (D o ) is between 0.061 and 0.071. The heat transfer tube includes multiple pluralities of adjacent helical fins protruding circumferentially around the interior surface of the tube body at respective helix angles. The multiple pluralities are separated by one or more transition area(s).

CROSS REFERENCE TO A RELATED APPLICATION

The application claims the benefit of U.S. Provisional Application No. 63/199,017 filed Dec. 2, 2020, the contents of which are hereby incorporated in their entirety.

BACKGROUND

The invention relates generally to heat transfer tubes for use in heat exchangers. In particular, the invention relates to a heat transfer tube that is configured to optimize its use within a heat exchanger for an air conditioner.

An air conditioner is a type of vapor compression system that is only capable of providing cooling (e.g., as opposed to a heat pump with is capable of switching between a heating mode and a cooling mode by reversing the flow of refrigerant). Vapor compression systems (e.g., air conditioners, heat pumps, etc.) commonly include a compressor to both move and increase the pressure of the refrigerant, two heat exchangers (one indoor heat exchanger and one outdoor heat exchanger) to transfer heat to or from the refrigerant, and at least one expansion valve for regulating the flow of refrigerant. In a basic air conditioner, the compressor compresses the refrigerant and delivers it downstream to the outdoor heat exchanger. The refrigerant is passed from the outdoor heat exchanger through the expansion valve to the indoor heat exchanger where heat is transferred from an indoor air supply to the refrigerant inside the indoor heat exchanger (i.e., to cool the indoor air supply). After transferring heat from the indoor air supply, the refrigerant is routed back into the compressor, completing the cycle.

In recent years, there has been a focus on improving the heat exchangers (both the indoor heat exchanger and the outdoor heat exchanger) to increase the efficiency of the air conditioners. Commonly, heat exchangers incorporate one or more tubes to circulate refrigerant and transfer heat to or from an air supply (e.g., for a residential home, etc.). This heat is transferred through the tube walls via conduction.

Many heat exchangers also utilize fins in thermally conductive contact with the outside of the tubes to provide increased surface area across which heat can be transferred. To improve the ability of the heat exchanger tubes to transfer heat through the tube walls, the tubes are often internally enhanced. These internally enhanced tubes are typically fabricated via an extrusion or drawings process and mechanically expanded into the fins to assure good metal-to-metal contact between the tubes and the fins. Often times copper, or alloys thereof, are used due to copper's mechanical properties, which enable helically shaped enhancement profiles to be fabricated with the extrusion process. However, in recent years, the industry has started to move from copper to aluminum, primary due to the fluctuating, often high, price of copper relative to aluminum. Aluminum, and alloys thereof, have inherently different mechanical properties that historically have limited its ability to be manufactured. In addition, due to the properties of the aluminum, historically, aluminum heat transfer tubes have a thicker tube wall (relative to tubes made of copper), which causes a smaller internal diameter, resulting in an increased pressure drop. As such, selecting an optimal configuration, that is capable of being manufactured, for an aluminum heat transfer tube often requires a balance between heat transfer improvement and pressure drop penalty. Although there are many different configurations of aluminum heat transfer tubes, new aluminum heat transfer tube configurations are always welcome.

Accordingly, there remains an ongoing need for new aluminum heat transfer tube configurations that are more efficient and capable of being more easily manufactured.

BRIEF DESCRIPTION

According to one embodiment, a heat transfer tube for operating in a cooling mode is provided. The heat transfer tube includes a tube body defining an interior surface and an exterior surface. The tube body defining an outer diameter (D_(o)) and a wall thickness (W_(T)), wherein a ratio (W_(T)/D_(o)) of the wall thickness (W_(T)) to the outer diameter (D_(o)) is between 0.061 and 0.071. The heat transfer tube includes a first plurality of adjacent helical fins protruding circumferentially around the interior surface of the tube body at a first fin helix angle, and a second plurality of adjacent helical fins protruding circumferentially around the interior surface of the tube body at a second fin helix angle. The heat transfer tube includes a transition area disposed between the first plurality of adjacent helical fins and the second plurality of adjacent helical fins. Each respective helical fin defining a fin height, a fin tip width, a fin base width, and a fin apex angle. At least one groove is disposed between the plurality of adjacent helical fins. The interior surface of the tube body further includes a non-fin weld area, the non-fin weld area defining a non-fin height and a non-fin width.

In accordance with additional or alternative embodiments, each respective helical fin includes a plurality of crosshatches configured in parallel with a longitudinal axis of the heat transfer tube.

In accordance with additional or alternative embodiments, each respective crosshatch defines at least one of: a crosshatch angle between 0° and 5°, a crosshatch v-angle between 38° and 49°, a crosshatch depth between 0.40 mm and 0.70 mm, a crosshatch pitch between 1.40 mm and 1.60 mm, and a crosshatch width between 0.12 mm and 0.26 mm.

In accordance with additional or alternative embodiments, the heat transfer tube provides a Cavallini factor between 1.67 and 2.22.

In accordance with additional or alternative embodiments, the tube body is made of at least one of: an aluminum and an aluminum alloy.

In accordance with additional or alternative embodiments, a cross-section of the heat transfer tube defines between 41 and 48 helical fins.

In accordance with additional or alternative embodiments, the outside diameter is between 6.85 mm and 7.14 mm, and the wall thickness is between 0.410 mm and 0.510 mm.

In accordance with additional or alternative embodiments, the fin height is between 0.144 mm and 0.248 mm, the fin tip width is between 0.096 mm and 0.156 mm, and the fin base width is between 0.18 mm and 0.24 mm.

In accordance with additional or alternative embodiments, the fin apex angle is between 19° and 35°, and the fin helix angles are between 13° and 23°.

In accordance with additional or alternative embodiments, the groove width is between 0.102 mm and 0.221 mm.

According to another aspect of the disclosure, a heat exchanger for operating in a cooling mode is provided. The heat exchanger includes a plurality of fins, and at least one heat transfer tube configured to pass a fluid therethrough. The at least one heat transfer tube extending through the plurality of fins. Each respective heat transfer tube includes a tube body defining an interior surface and an exterior surface. The tube body defining an outer diameter (D_(o)) and a wall thickness (W_(T)), wherein a ratio (W_(T)/D_(o)) the wall thickness (W_(T)) to the outer diameter (D_(o)) is between 0.061 and 0.071. Each respective heat transfer tube includes a first plurality of adjacent helical fins protruding circumferentially around the interior surface of the tube body at a first fin helix angle, and a second plurality of adjacent helical fins protruding circumferentially around the interior surface of the tube body at a second fin helix angle. A transition area is disposed between the first plurality of adjacent helical fins and the second plurality of adjacent helical fins. Each respective helical fin defining a fin height, a fin tip width, a fin base width, and a fin apex angle, at least one groove disposed between the plurality of adjacent helical fins. The interior surface of the tube body further includes a non-fin weld area, the non-fin weld area defining a non-fin height and a non-fin width.

In accordance with additional or alternative embodiments, each respective helical fin includes a plurality of crosshatches configured in parallel with a longitudinal axis of the heat transfer tube.

In accordance with additional or alternative embodiments, each respective crosshatch defines at least one of: a crosshatch angle between 0° and 5°, a crosshatch v-angle between 38° and 49°, a crosshatch depth between 0.40 mm and 0.70 mm, a crosshatch pitch between 1.40 mm and 1.60 mm, and a crosshatch width between 0.12 mm and 0.26 mm.

In accordance with additional or alternative embodiments, the heat transfer tube provides a Cavallini factor between 1.67 and 2.22.

In accordance with additional or alternative embodiments, the tube body is made of at least one of: an aluminum and an aluminum alloy.

In accordance with additional or alternative embodiments, a cross-section of the heat transfer tube defines between 41 and 48 helical fins.

In accordance with additional or alternative embodiments, the outside diameter is between 6.85 mm and 7.14 mm, and the wall thickness is between 0.410 mm and 0.510 mm.

In accordance with additional or alternative embodiments, the fin height is between 0.144 mm and 0.248 mm, the fin tip width is between 0.096 mm and 0.156 mm, and the fin base width is between 0.18 mm and 0.24 mm.

In accordance with additional or alternative embodiments, the fin apex angle is between 19° and 35°, and the fin helix angles are between 13° and 23°.

In accordance with additional or alternative embodiments, the groove width is between 0.102 mm and 0.221 mm.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter, which is regarded as the disclosure, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The following descriptions of the drawings should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:

FIG. 1 is a perspective view of an exemplary heat exchanger incorporating an exemplary heat exchanger tube, in accordance with one aspect of the disclosure.

FIG. 2 is a perspective side view of the exemplary heat exchanger tube of FIG. 1, in accordance with one aspect of the disclosure.

FIG. 3 is a cross-sectional front view of the exemplary heat exchanger tube of FIGS. 1 and 2 illustrating multiple pluralities of adjacent helical fins protruding circumferentially around the interior surface of the tube body at particular respective helix angles, with transition areas disposed between respective pluralities of adjacent helical fins, in accordance with one aspect of the disclosure.

FIG. 4 is a perspective view of the interior surface of the tube body, prior to being rolled and forged into the circular configuration shown in FIG. 3, illustrating the multiple pluralities of adjacent helical fins separated by the transition areas, in accordance with one aspect of the disclosure.

FIG. 5 is a cross-sectional view of a portion of the exemplary heat exchanger tube of FIGS. 1-3 illustrating the plurality of adjacent helical fins from a closer perspective, in accordance with one aspect of the disclosure.

FIG. 6 is a cross-sectional view of a portion of the exemplary heat exchanger tube of FIGS. 1-3 illustrating a non-fin weld area disposed on the interior surface of the tube body, in accordance with one aspect of the disclosure.

FIG. 7 is a cross-sectional view of a portion of the exemplary heat exchanger tube of FIGS. 1-3 illustrating a plurality of crosshatches, in accordance with one aspect of the disclosure.

DETAILED DESCRIPTION

As will be described below, a heat transfer tube with improved efficiency and manufacturability, and a heat exchanger incorporating the same are provided. Specifically, the features of the heat transfer tube described herein may enable a more efficient operation for an air conditioner, which is capable of operating in a cooling mode. The heat transfer tube described herein has an optimal configuration that balances the heat transfer improvement (in condensation) with the associated pressure drop penalty. It was found that the configuration of the different features of the heat transfer tube described herein results in a surprisingly high performance when compared to other designs currently used in the industry.

It will be appreciated that this surprisingly high performance is directly tied to the use of the heat transfer tube within an air conditioner, which is only capable of operating in a cooling mode. For example, the heat transfer tube described herein may not be optimized for use within a system that is capable of providing both cooling and heating (e.g., such as a heat pump). It will be appreciated that the heat transfer tube described herein may be made of aluminum (or alloy thereof), and may only be manufactured using a welded-rolled formed process (e.g., compared to an extrusion process commonly used to manufacture heat transfer tubes made of copper or copper alloys) in certain instances. The manufacturing process of the heat transfer tube is described in further detail below. It is envisioned that by manufacturing the heat transfer tube out of aluminum (or aluminum alloy), instead of copper, that the associated costs of manufacturing the heat transfer tube may be more predictable and relatively lower (when compared to heat transfer tubes made of copper or copper alloys).

With reference now to the Figures, a perspective view of an exemplary heat exchanger 200 incorporating an exemplary heat exchanger tube 100 is shown in FIG. 1. As shown, the heat exchanger 200 may be a round tube plate fin (RTPF) type heat exchanger, including a plurality of fins 210 and at least one heat transfer tube 100. For purposes of clarity, although the heat exchanger 200 is shown to include only one heat transfer tube 100, which is shown to include an inlet line 130 at one end, an outlet line 140 connected at another end, and a bend 150 therebetween, it will be evident to a person of ordinary skill in the art, that more heat transfer tubes 100 may be added to the heat exchanger 200. It should be appreciated that the heat transfer tube 100 may be separated in multiple sections (e.g., where the bend 150 portion is connected to the inlet line 130 and the outlet line 140) in certain instances, or formed as a single tube unitary tube in other instances.

As mentioned above, the heat transfer tube(s) 100 may be made of an aluminum or an aluminum alloy in certain instances. For example, the heat transfer tube(s) 100 may be made from aluminum alloys selected from 1000 series, 3000 series, 5000 series, or 600 series aluminum alloys in certain instances. Likewise, the fins 210 too may be made of an aluminum or an aluminum alloy in certain instances. For example, the fins 210 may be made from aluminum alloys selected from the 1000 series, 3000 series, 6000 series, 7000 series, or 8000 series aluminum alloys in certain instances. It will be appreciated that the fins 210 and/or the heat transfer tube(s) 100 may be made from other aluminum alloys in certain instances. Regardless of the type of material(s) used to manufacture the fins 210 and/or the heat transfer tube(s) 100, the fins 210 may be configured as plate-like elements spaced along the length of the heat transfer tube(s) 100 (e.g., using an interference fit in certain instances).

As shown in FIG. 1, the fins 210 may be provided between a pair of end plates or tube sheets 220, 230. It is envisioned that the fins 210 may help to increase the surface area for which heat may be transferred between the refrigerant (circulating through the heat transfer tube(s) 100) and the air passing over the heat exchanger 200. As mentioned above, the heat transfer tube(s) 100 may be specifically designed to increase the efficiency of an air conditioner, which is only capable of operating in a cooling mode. It will be evident to a person of ordinary skill in the art, that the heat transfer tube(s) 100 may not be optimal for use within a system that is capable of operating in both a heating mode and a cooling mode (e.g., such as a heat pump).

It will be appreciated that the increase in efficiency of the air conditioner caused by the heat transfer tube(s) is attributable to the configuration of the different features of the heat transfer tube(s) 100. An exemplary heat transfer tube 100 is shown in FIGS. 2-4. FIG. 2 is provided to illustrate the heat transfer tube 100 without the plurality of fins 200 (as shown in FIG. 1). FIG. 3 is provided to illustrate the interior surface 121 and the exterior surface 122 of the tube body 120. FIG. 4 is provided to illustrate the interior surface of the tube body 120, prior to being rolled and forged in the circular configuration shown in FIG. 3. As shown in FIG. 3, the tube body 120 may define an outer diameter D_(o) and a wall thickness W_(T) (also shown in FIG. 5). It was found that by controlling the ratio (W_(T)/D_(o)) of the wall thickness W_(T) to the outer diameter D_(o) that the heat transfer tube 100 may be optimized for use within an air conditioner. In certain instances the ratio (W_(T)/D_(o)) of the wall thickness W_(T) to the outer diameter D_(o) is between 0.061 and 0.071.

As shown in FIGS. 3 and 4, the heat transfer tube 100 includes at least two pluralities 115 of adjacent helical fins 110 (shown in FIG. 5) protruding circumferentially around the interior surface 121 of the tube body 120. For example, as shown in FIG. 4, the heat transfer tube 100 may include a first plurality 115(a) of adjacent helical fins 110 protruding around the interior surface 121 of the tube body 120 at a first fin helix angle Θ_(HA1), and a second plurality 115(b) of adjacent helical fins 110 protruding around the interior surface 121 of the tube body 120 at a second fin helix angle Θ_(HA2). The first fin helix angle Θ_(HA1) and the second fin helix angle Θ_(HA2) may be complimentary and equal to one another so as to form a ‘V’ configuration (which may be inverted in certain instances). Although described herein that the heat transfer tube 100 may include at least two pluralities 115 of adjacent helical fins 110, it should be appreciated that the heat transfer tube 100 may include any even number (e.g., two, four, six, etc.) of pluralities 115, each with their own respective fin helix angle Θ_(HA(n)) (which, as mentioned above, may be complimentary and equal to one another so as to form ‘V’ configurations between adjacent pluralities 115). As shown in FIGS. 3 and 4, the multiple pluralities 115(a)-(d) are separated by transition areas 180 (which may have a minimum width so as to sufficiently separate the pluralities 115(a)-(d) from one another). In certain instances the transition area 180 is between 0.50 mm and 0.80 mm wide. It should be appreciated that adjacent pluralities 115 (each with their own respective fin helix angles Θ_(HA(n))) may directly abut one another in certain instances (i.e., meaning that the transition areas 180 may have a width of approximately 0 mm). When directly abutting one another, the transition areas 180 may be defined as an axis at which the fin helix angles Θ_(HA(n)) switch from one direction to another so as to form the ‘V’ configuration between the adjacent pluralities 115.

As shown in FIG. 5, at least one groove 160 (viewed as the void or space between adjacent fins 110) may be disposed between adjacent helical fins 110. Each respective groove may be viewed to have a defined groove width W_(G). Each respective helical fin 110 may be viewed to have a defined fin height H_(F), fin tip width W_(FT), fin base width W_(FB), fin apex angle Θ_(FA), and fin helix angle Θ_(HA) (shown in FIG. 4). In addition, the interior surface 121 of the tube body 120 may also include a non-fin weld area 170 (shown in FIGS. 3 and 6). It should be appreciated that this non-fin weld area 170 may be a result of the welded-rolled formed manufacturing process used to produce the heat transfer tube 100 described herein. As shown in FIGS. 3 and 6, the non-fin weld area 170 may be viewed to have a defined non-fin height H_(NF) and non-fin width W_(NF).

As mentioned above, the heat transfer tube 100 described herein may be manufactured using a welded rolled formed manufacturing process. This process may include starting with a rectangular sheet of aluminum (or alloy thereof) that is manufactured to include fins 110 (e.g., which, as described above, may be configured in different pluralities 115 with respective fin helix angles Θ_(HA)). An exemplary rectangular sheet with multiple pluralities 115 is shown in FIG. 4. This rectangular sheet of aluminum (or alloy thereof) is rolled using a rolling machine into a tubular shape. These rolling machines may utilize a high-frequency electrical current to forge the seam or joint of the heat transfer tube 100. It should be appreciated that other methods may be used to forge the seam or joint of the heat transfer tube 100 (e.g., tig-type, mig-type, or any suitable electrical-type welding, etc. may be used in certain instances).

The non-fin weld area 170 described above may be viewed as this seam or joint of the heat transfer tube 100. Although described as a non-fin weld area 170, it will be appreciated that partial or irregular fins 110 may be present within the non-fin weld area 170. These partial or irregular fins 110 may be caused as a result of the welding process, which may consume or distort the fins 110 from their original form (i.e. how they existed on the rectangular sheet of aluminum). It should be appreciated that the dimensions of the non-fin weld area 170 may be directly associated with the limitations of the welded rolled formed manufacturing process. For example, although it may be ideal to minimize the non-fin height H_(NF) and/or the non-fin width W_(NF) in order to maximize the number of helical fins 110 and/or internal surface area within the heat transfer tube 100, the welded rolled formed manufacturing process inherently requires at least a certain sized non-fin weld area 170. In certain instances the non-fin width W_(NF) should be less than 1.4 mm. It should be appreciated that the non-fin weld area 170 should be ignored with respect to average fin and average wall thickness W_(T) in certain instances. It will be evident to a person of ordinary skill in the art that the non-fin weld area 170 is created a result of a welded rolled formed manufacturing process and not created by any irregularities from an extrusion-type manufacturing process.

As mentioned above, the heat transfer tube 100 described herein is optimized for use within an air conditioner, which is only capable of operating in a cooling mode. It was found when optimizing the heat transfer tube 100 for use within an air conditioner the heat transfer tube 100 provides a Cavallini factor between 1.67 and 2.22 in certain instances. The Cavallini factor may be expressed in terms of the following formula: [[2*(number of fins)*(height of the fins)*(1−Sin(Θ_(FA)/2))/((3.14)(internal diameter of the heat transfer tube)*Cos(Θ_(FA)/2))+1]/Cos Θ_(HA)]{circumflex over ( )}2. To produce such a heat transfer tube 100 with such a Cavallini factor, the tube body 120 and the helical fins 110 should be precisely configured. For example, the cross-section of the heat transfer tube 100 should define between 41 and 48 helical fins 110 (i.e., when viewed from the front of the heat transfer tube 100). It will be appreciated that the heat transfer tube 100 described herein may have 48 helical fins 110 in certain instances.

It is envisioned that the heat transfer tube 100 described herein may be configured to minimize its outside diameter D_(o) (shown in FIG. 3), while maximizing its internal diameter (i.e. D_(o)-W_(T)), which may help minimize the pressure drop generated by the heat transfer tube 100. The outside diameter D_(o) is between 6.85 mm and 7.14 mm and the wall thickness W_(T) (shown in FIG. 3) is between 0.410 mm and 0.510 mm in certain instances. It will be appreciated that the outside diameter D_(o) is less than 7.10 mm (e.g., 7.05 mm) and the wall thickness W_(T) is less than 0.50 mm (e.g., 0.46 mm) in certain instances, which may help minimize the pressure drop generated by the heat transfer tube 100. To effectively function within the air conditioner, the heat transfer tube 100 should not only be configured to minimize pressure drop, but should also be configured to maximize its heat transfer capabilities (in condensation). As shown above by the formula for the Cavallini factor, the Cavallini factor (which is illustrative of the heat transfer capabilities of the heat transfer tube 100) is dependent, at least in part, on the configuration of the helical fins 110.

As shown in FIG. 5, each respective helical fin 110 may be viewed to have a defined fin height H_(F), fin tip width W_(FT), fin base width W_(FB), fin apex angle Θ_(FA), and fin helix angle Θ_(HA) (shown in FIG. 4). The fin height H_(F) is between 0.144 mm and 0.248 mm (e.g., 0.23 mm) in certain instances. The fin tip width W_(FT) is between 0.096 mm and 0.156 mm (e.g., 0.11 mm) in certain instances. The fin base width W_(FB) is between 0.18 mm and 0.24 mm (e.g., 0.21 mm) in certain instances. The fin apex angle Θ_(FA) is between 19° and 35° (e.g., 25°) in certain instances. The fin helix angle Θ_(HA) is between 13° and 23° (e.g., 18°) in certain instances. As shown in FIG. 4, the groove(s) 160, disposed between the helical fins 110, may be viewed to have a defined groove width W_(G). The groove width W_(G) is between 0.102 mm and 0.221 mm (e.g., 0.19 mm) in certain instances.

As shown in FIGS. 3, 4, and 7, each respective helical fin 110 may include a plurality of crosshatches 190 configured in parallel (e.g., +/−5°) with the longitudinal axis T_(LA) of the heat transfer tube 100 in certain instances. These crosshatches 190 were found to be especially useful in increasing the heat transfer capabilities (for condensation) of the heat transfer tube 100. As shown, each respective crosshatch 190 may be viewed to have a defined crosshatch angle Θ_(CA) (shown in FIG. 4, measured from the longitudinal axis T_(LA) of the heat transfer tube 100), crosshatch v-angle Θ_(VA), crosshatch depth D_(C), crosshatch pitch P_(C), and crosshatch width W_(C). The crosshatch angle Θ_(CA) is between 0° and 5° from the longitudinal axis T_(LA) of the heat transfer tube 100 in certain instances. The crosshatch v-angle Θ_(VA) is between 38° and 49° in certain instances. The crosshatch depth D_(C) is between 0.40 mm and 0.70 mm in certain instances. The crosshatch pitch P_(C) is between 1.40 mm and 1.60 mm in certain instances. The crosshatch width W_(C) is between 0.12 mm and 0.26 mm in certain instances.

It will be evident to a person of ordinary skill in the art that the dimensions described above are given in respect to the heat transfer tube 100 prior to joining with the plurality of fins 210, which may be joined using pressure expansion or mechanical expansion (either of which may cause deformation of one or more of the dimensions). It should be appreciated that the configuration of the fins 110 and the grooves 160, as described above, were selected so as to optimize the function of the heat transfer tube 100 within an air conditioner, which, as mentioned above, is only capable of operating in a cooling mode. As such, the heat transfer tube 100 describe herein may not be optimized for use within a system that is capable of switching between a heating mode and a cooling mode, such as a heat pump.

The use of the terms “a” and “and” and “the” and similar referents, in the context of describing the invention, are to be construed to cover both the singular and the plural, unless otherwise indicated herein or cleared contradicted by context. The use of any and all example, or exemplary language (e.g., “such as”, “e.g.”, “for example”, etc.) provided herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed elements as essential to the practice of the invention.

While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims. 

What is claimed is:
 1. A heat transfer tube for operating in a cooling mode, the heat transfer tube comprising: a tube body comprising an interior surface and an exterior surface, the tube body defining an outer diameter (D_(o)) and a wall thickness (W_(T)), wherein a ratio (W_(T)/D_(o)) of the wall thickness (W_(T)) to the outer diameter (D_(o)) is between 0.061 and 0.071; and a first plurality of adjacent helical fins protruding circumferentially around the interior surface of the tube body at a first fin helix angle, and a second plurality of adjacent helical fins protruding circumferentially around the interior surface of the tube body at a second fin helix angle, a transition area disposed between the first plurality of adjacent helical fins and the second plurality of adjacent helical fins, each respective helical fin defining a fin height, a fin tip width, a fin base width, and a fin apex angle, at least one groove disposed between the plurality of adjacent helical fins, wherein the interior surface of the tube body further comprises a non-fin weld area, the non-fin weld area defining a non-fin height and a non-fin width.
 2. The heat transfer tube of claim 1, wherein each respective helical fin comprises a plurality of crosshatches configured in parallel with a longitudinal axis of the heat transfer tube.
 3. The heat transfer tube of claim 2, wherein each respective crosshatch defines at least one of: a crosshatch angle between 0° and 5°, a crosshatch v-angle between 38° and 49°, a crosshatch depth between 0.40 mm and 0.70 mm, a crosshatch pitch between 1.40 mm and 1.60 mm, and a crosshatch width between 0.12 mm and 0.26 mm.
 4. The heat transfer tube of claim 1, wherein the heat transfer tube provides a Cavallini factor between 1.67 and 2.22.
 5. The heat transfer tube of claim 1, wherein the tube body is comprised of at least one of: an aluminum and an aluminum alloy.
 6. The heat transfer tube of claim 1, wherein a cross-section of the heat transfer tube defines between 41 and 48 helical fins.
 7. The heat transfer tube of claim 1, wherein the outside diameter is between 6.85 mm and 7.14 mm, and the wall thickness is between 0.410 mm and 0.510 mm.
 8. The heat transfer tube of claim 1, wherein the fin height is between 0.144 mm and 0.248 mm, the fin tip width is between 0.096 mm and 0.156 mm, and the fin base width is between 0.18 mm and 0.24 mm.
 9. The heat transfer tube of claim 1, wherein the fin apex angle is between 19° and 35°, and the fin helix angles are between 13° and 23°.
 10. The heat transfer tube of claim 1, wherein the groove width is between 0.102 mm and 0.221 mm.
 11. A heat exchanger for operating in a cooling mode, the heat exchanger comprising: a plurality of fins; and at least one heat transfer tube configured to pass a fluid therethrough, the at least one heat transfer tube extending through the plurality of fins, each respective heat transfer tube comprising: a tube body comprising an interior surface and an exterior surface, the tube body defining an outer diameter (D_(o)) and a wall thickness (W_(T)), wherein a ratio (W_(T)/D_(o)) the wall thickness (W_(T)) to the outer diameter (D_(o)) is between 0.061 and 0.071; and a first plurality of adjacent helical fins protruding circumferentially around the interior surface of the tube body at a first fin helix angle, and a second plurality of adjacent helical fins protruding circumferentially around the interior surface of the tube body at a second fin helix angle, a transition area disposed between the first plurality of adjacent helical fins and the second plurality of adjacent helical fins, each respective helical fin defining a fin height, a fin tip width, a fin base width, and a fin apex angle, at least one groove disposed between the plurality of adjacent helical fins, wherein the interior surface of the tube body further comprises a non-fin weld area, the non-fin weld area defining a non-fin height and a non-fin width.
 12. The heat exchanger of claim 11, wherein each respective helical fin comprises a plurality of crosshatches configured in parallel with a longitudinal axis of the heat transfer tube.
 13. The heat exchanger of claim 12, wherein each respective crosshatch defines at least one of: a crosshatch angle between 0° and 5°, a crosshatch v-angle between 38° and 49°, a crosshatch depth between 0.40 mm and 0.70 mm, a crosshatch pitch between 1.40 mm and 1.60 mm, and a crosshatch width between 0.12 mm and 0.26 mm.
 14. The heat exchanger of claim 11, wherein the heat transfer tube provides a Cavallini factor between 1.67 and 2.22.
 15. The heat exchanger of claim 11, wherein the tube body is comprised of at least one of: an aluminum and an aluminum alloy.
 16. The heat exchanger of claim 11, wherein a cross-section of the heat transfer tube defines between 41 and 48 helical fins.
 17. The heat exchanger of claim 11, wherein the outside diameter is between 6.85 mm and 7.14 mm, and the wall thickness is between 0.410 mm and 0.510 mm.
 18. The heat exchanger of claim 11, wherein the fin height is between 0.144 mm and 0.248 mm, the fin tip width is between 0.096 mm and 0.156 mm, and the fin base width is between 0.18 mm and 0.24 mm.
 19. The heat exchanger of claim 11, wherein the fin apex angle is between 19° and 35°, and the fin helix angles are between 13° and 23°.
 20. The heat exchanger of claim 11, wherein the groove width is between 0.102 mm and 0.221 mm. 